A drum brake system is a common type of brake system. Drum brakes generally include opposing brake shoes that are moved away from one another and into engagement with an inner surface of a brake drum to create an expansion force to slow or stop a moving vehicle. A drum-in-hat system is another type of brake system that combines a disc brake system and a drum brake system. The disc brake system includes opposing brake pads that are moved towards each other and into engagement with a brake rotor to create a clamping force to slow or stop a moving vehicle. In drum-in-hat systems, the drum brake system is used as a parking brake to create the expansion force necessary to maintain the vehicle in a stopped or parked position by moving brake shoes into engagement with an inner surface of the brake rotor (i.e., a drum portion).
Some parking brake systems use an actuator assembly to move the brake shoes into engagement with the brake drum and/or the drum portion of as brake rotor to create the expansion force during a parking brake apply. The actuator assembly is also used to move the brake shoes out of engagement with the brake drum and/or the drum portion of the brake rotor to release the expansion force. Some parking brake systems, actuator assemblies, or both use a position sensor to track brake shoe wear and to verify that the brake shoes return to a home position after the parking brake is released. To reduce cost and space, and to comply with updated recommendations, it may be desirable to provide as brake system that does not include as position sensor. That is, it may be desirable to have an actuator assembly that includes a mechanism or device other than a position sensor to monitor brake shoe wear and to verify that the brake shoes return to a home position after release of the parking brake. It may be attractive to have an actuator assembly for a parking brake system that can be easily incorporated into a conventional brake system, such as a drum brake system, a drum-in-hat brake system, or both. It would be desirable to provide an actuator assembly for as parking brake system that is reliable, can be mass-produced relatively inexpensively, that has a minimal number of parts, and is easy to operate.
An example of a parking brake system is disclosed in U.S. Patent Application Publication No. 2014/0345989, and an example of an actuator for a parking brake system is disclosed in U.S. Pat. No. 8,011,482 B2, both of which are expressly incorporated by reference herein for all purposes.